1. Field of the Invention
The present invention relates to novel allosamidin compounds which are useful in the fields of agricultural chemicals, animal and human drugs, etc., compositions containing the novel allosamidin compounds, and processes for the production of the novel allosamidin compounds.
2. Discussion of the Background
Chitin is the main component of cell walls. During division and proliferation of fungi, the synthesis of chitin is well-balanced with its decomposition. Chitin is also the principal component found in the exoskeletons of insects. The synthesis and decomposition of chitin are also elaborately controlled in the process where insects cast the skin and grow.
Chitinase is the major enzyme which participates in the metabolism of chitin. Inhibitors of this enzyme represent a new class of antifungal agents and/or insect growth control agents.
Heretofore, three chitinase inhibitors were known: allosamidin (S. Sakuda et al., J. Antibiotics, vol. 40, pp. 296-300, 1987), methylallosamidin (S. Sakuda et al., Preprint of 28th Discussions and Lectures on Natural Organic Compounds, p. 70, 1986) and demethylallosamidin (S. Sakuda et al., Agric. Biol. Chem., vol. 54, pp. 1333-1335, 1990).
Among them, allosamidin and methylallosamidin are inhibitors of silkworm-derived chitinase. These compounds also strongly inhibit the endo-type chitinase of insects, but show a weak inhibitory activity against fungi-derived chitinase. Demethylallosamidin shows a potent inhibitory activity against chitinase from baker's yeast (Saccharomyces cerevisiae), but its inhibitory activity against the chitinase of pathogenic fungi such as Candida albicans is insufficient for its use as an anti-fungal agent. Thus, a more potent and/or broader-spectrum chitinase inhibitor is desired.
The three substances described above all have a pseudo trisaccharide structure, composed of two 2-amino-2-deoxy-D-allose (or N-acetylallosamine) molecules and one allosamizoline (or demethylallosamizoline) molecule. These compounds represent the first time N-acetylallosamine has been found as a constituent in a natural product. To date, no other natural source of allosamidin has been found. Accordingly, there is no abundant supply of these compounds. Furthermore, no industrially useful synthesis of allosamine or compound containing allosamine is known.
To meet the needs for (1) a more potent chitinase inhibitor, (2) a chitinase inhibitor which exhibits inhibitory activity against a broad spectrum of chitinases (that is, chitinases from a variety of sources), and (3) an industrially useful synthesis of allosamine and/or compounds containing allosamine, the present Inventors have discovered and investigated novel allosamidin compounds, AJI9463A, AJI9463B and AJI9463C, produced by microorganisms belonging to the genus Streptomyces, and partially-hydrolyzed disaccharides thereof. These compounds have been shown to have potent inhibitory activity against chitinase from a number of sources, and have anti-fungal activity against pathogenic fungi.